The present invention relates to a droplet ejection apparatus having a droplet ejection head, a method for recovering a droplet ejection head, a method for forming a thin film using a droplet ejection apparatus, and a liquid crystal display.
As a droplet ejection apparatus having a droplet ejection head, an inkjet type recording apparatus that ejects ink, which is liquefied material, from an inkjet head onto a recording paper sheet is known.
The recording apparatus can have printing problems if the ink dries in nozzles of the inkjet head, causing nozzle clogging or offset ejection of the ink. Therefore, to stabilize image quality provided by the apparatus, the dry ink is removed from nozzles of a nozzle forming surface of the inkjet head by drawing the ink from the nozzles, with a cap, or a sealing member, held in tight contact with the nozzle forming surface. Also, the nozzle forming surface is wiped by a wiping member to remove the ink or foreign matter from the nozzle forming surface. Such operations are referred to as recovery, refreshment, or cleaning of the inkjet head.
JP-A-2003-127400 discloses a cap having a retainer portion provided in a bottom portion of a cap casing. The retainer portion retains liquid that generates vapor. When the recording apparatus is in a nonoperating state, the cap casing is maintained in tight contact with a nozzle forming surface. This prevents dryness of the ink in nozzles and the vicinity of the nozzles.
JP-A-2003-001839 discloses an apparatus that performs recovery of an inkjet head by pressing a rigid cap against an elastic seal material, which is arranged in an inkjet head in such a manner as to encompass a nozzle forming surface. Through such pressing of the cap against the seal member, the nozzle forming surface is sealed with improved air-tightness.
As described in JP-A-2003-127400, the cap is formed of semi-rigid synthetic rubber. Likewise, as described in JP-A-2003-001839, the elastic seal member, which is held in contact with the rigid cap, is formed of rubber or the like. Therefore, if the ink adheres to the cap or the seal member formed of rubber, the cap or the seal member may deteriorate, which lowers sealing performance of the cap or the seal member. Further, such deterioration may separate a portion from the cap or the seal member, causing the portion to adhere to the nozzle forming surface.
Further, a droplet ejection method for forming a thin film on a surface of a workpiece by ejecting, instead of ink, liquefied material containing functional material from a droplet ejection head onto the workpiece now draws attention. The liquefied material contains a specific solvent selected in correspondence with the functional material. If capping devices described in the aforementioned documents are employed in the droplet ejection head that ejects the liquefied material containing the functional material, deterioration of the cap or the elastic seal member, which are formed of rubber, becomes increasingly significant depending on properties of the solvent.
Further, when the nozzle forming surface is sealed by the cap, the nozzle forming surface is exposed to the air in the sealed space defined by the cap. In this state, the liquefied material in the nozzles becomes progressively dry. Therefore, if the nozzle forming surface is maintained in a state sealed by the cap for an excessively long time, nozzle clogging or offset ejection of the ink can occur.